1. Field of the Invention
The present invention relates to an on-line character recognition method and device, and more particularly to an on-line character recognition method and device that recognizes inputted characters on-line by finding inter-stroke distance in the patterns in stroke units of inputted characters and reference patterns in stroke units that are produced in advance by quantizing the strokes of target characters.
2. Description of the Related Art
Japanese Patent Publication No. 38351/93 (Hereinbelow referred to as Reference 1) discloses one example of an on-line character recognition device that recognizes characters on-line by using information regarding strokes, a stroke being a continuous pen track from the contact of a pen with a tablet until separation of the pen from the tablet.
In this on-line character recognition device, patterns in stroke units are first found from inputted characters, and then, using a stroke code book composed of assemblages of reference patterns prepared in advance by quantizing the strokes of target characters, inter-stroke distances are found with respect to each of the reference patterns in the stroke code book. Next, inter-character distances are found by adding each of the obtained inter-stroke distances in accordance with a character dictionary in which characters are represented by code strings for each reference pattern within the stroke code book, and the character giving the smallest distance is taken as the recognition result. This method allows a reduction in both the amount of memory and number of calculations as compared with a case in which inter-stroke distances for all strokes are calculated without quantizing the strokes of target characters.
The method described in the paper "Application of Fuzzy Logic in an On-line Handwritten Character Recognition Method" in the Papers of the Institute of Electronics, Information and Communication Engineers (February 1991, D-II, Vol. J74-D-II, No. 2, pp. 166-174) (Hereinafter referred to as Reference 2) seeks the degree of similarity between the shape of each stroke of an inputted character and each of a number of basic stroke shape patterns prepared in advance. Characters are recognized using a recognition dictionary of character units described in terms of fuzzy propositions using this degree of similarity and each of various features. The character dictionary may take a form in which, for example, every character is described in terms of fuzzy propositions using the various features such as stroke shape, stroke length, stroke direction, stroke position, and number of stroke; two examples being "the first line is close to representative stroke pattern No. 1 or representative stroke pattern No. 2" and "the beginning of the second line is close to and below the beginning of the first line."
In the prior-art device described in Reference 1, the patterns of stroke units are quantized without alteration and therefore include information on stroke shape and position. Patterns of differing position but of similar shape are therefore prepared as different stroke unit patterns, and this prior-art method therefore necessitates a voluminous stroke code book, a huge amount of memory for maintaining the stroke code book, and numerous calculations for finding inter-stroke distances.
In the method described in Reference 2, there is the problem that a recognition dictionary must be prepared relating to each of different characteristics for every character. The production of these recognition dictionaries requires operator input for each individual character, and therefore necessitates a great deal of labor. Finally, there is the problem that control of the recognition process requires a complicated process of solving fuzzy propositions for every character, and this type of process is difficult to realize a high-speed and repetitive process by hardware.